Big phones, phablets, or whatever term you want to call them - the big-screen category is here to stay. The Samsung Galaxy Note 4 represents not only the most crucial big-screen device from the Korean company for a couple of years but, sub-genres brushed to one side for a moment, perhaps the most crucial smartphone in its line-up too.

Samsung created the big-screen phone category, and until now it's not had too much serious competition. In 2014 things are different: competitors are following where Samsung leads, with Apple's iPhone 6 Plus dipping into a similar concept and even the Huawei Ascend Mate 7 making a strong case.

Does Samsung need to worry about the Cupertino or Chinese giants eating into its very domain? The Note is a little different as it remains the only device of the three mentioned to offer a built-in stylus, otherwise known as the S Pen, and like a doting parent Samsung has shaped the Galaxy Note 4's user experience into something altogether more refined - and more complex.

Even so, if there's one thing Samsung just can't shake it's the apparent delight it has in opting for plasticky removable backs in the build, which is something more or less absent in among its peers, including HTC, Sony, Apple, et al. Does such a design quirk cost this big-screen device from remaining king of the phablet castle, or has Samsung got it all sewn-up for its third-generation Note?

No longer so large

When the original Galaxy Note launched many scoffed at the premise of a giganta-phone. But it did exceptionally well as has become part of the fabric of the smartphone market, inspiring many to follow.

In just three short years since the original, the Note 4 arrives and it no longer feels too large in today's market despite the 5.7-inch screen perhaps suggesting otherwise. How times change. The phone measures 153.5 x 78.6mm front-on, but that's a smaller face than the slightly slimmer iPhone 6 Plus (158.1 x 77.8mm) - and that's despite the Samsung donning the larger and higher-resolution screen of the pair.

Having used the Huawei Ascend Mate 7 for a full month we're well versed in big-phones. Shifting down a size to the Samsung Galaxy Note 4 doesn't feel drastically smaller (see in our gallery for side-by-side comparisons), but does feel like a slightly better-balanced arrangement, if the 176g weight doesn't bother you. For our money, Samsung has got the size just right and we've had no issues making of receiving calls.

At 8.5mm thick the Note 4 is relatively slim by today's standards, and while there are slimmer competitors the Note's rigid build has a perfect excuse: it includes that built-in S Pen stylus, which can be easily extracted or stowed in a cavity in the body. Very few competitors have gone down this route, but it's one of the selling points of the phone, whether you use it a little or use it a lot. More about that, related menus and handwriting features later.

There's 32GB of internal storage on board and a microSD card slot around the back for expansion up to a further 128GB. Also included is 50GB of Dropbox allocation for two years to store all those files.

Design quirks

Three days of use into using the Note 4 and we like its design. The grippy back, the solid construction, the more pocket-friendly size than it may sound. But it's not quite the perfect phone for a number of nit-picking reasons.

Although the hideous faux stitching and fake leather of the previous Note 3 has gone, the Note 4's removable plastic rear panel tries to hide its genetic makeup with a textured finish. It's fine, it's inoffensive, but this is a £629 device and such plastics are not a patch on the aluminium iPhone 6 Plus, curved metal of the Huawei Ascend Mate 7, or even the tempered glass of the Sony Xperia Z3.

Fortunately the rest of the Samsung design is elevated to a higher standards: the slender bezel to the side of the display, a sturdy metal frame holding everything together, and shiny metal buttons to control volume and power. We would have adjusted the button positioning, however, as for one-handed use the power/lock button is a little high, while the presence of volume up/down on the opposite side of the frame is far too high for one-handed adjustment.

Within the menus it's possible to align the virtual keyboard and number pad more towards the left or right side of the screen, which is a nice touch for left- or right-handed users, but for our hands wasn't something we found necessary. If you find you do need this adjustment then you'll probably find the physical keys to be awkwardly positioned.

Fingerprint fun and failures

Another notable design point is Samsung's home key - which is straddled by light-up "back" and "menu" Android soft keys to either side - that resides off the main screen display. It protrudes from the device unlike many other Android devices that opt for a trio of soft keys, but this has the benefit of avoiding eating into Note 4's screen real-estate.

Plus this physical home key houses the fingerprint scanner. But after using it for two days as a security lock to access the device, we switched it off. With it positioned so low in the design, swiping it with success when held in one hand frequently fails. In this size of phone it's just unwieldy and hard to use. For PayPal payments (it's officially approved) and so forth we give it the thumbs up, but for screen lock it became a hindrance rather than a useful addition.

Again it's the competition that sees the Samsung scanning method lag behind. The rear-positioned one on the Mate 7 is a far better implementation that works with a rested finger, not a swipe, and we've had much greater success with that. Outside of Android there's also Apple's Touch ID that we've found to be successful (even if, similarly, its placement on the home key on the large 6 Plus isn't always ideal).

Super screen

If there's one thing worth gushing about, though, then it's the Galaxy Note 4's screen. The 5.7-inch Super AMOLED panel has a whopping 1440 x 2560 pixel resolution, delivering a 515ppi pixel density. It's similar to that of the LG G3, despite being slightly larger overall, but is among the best smartphone screens on the market right now. And it's very impressive.

We didn't think it would make a dramatic amount of difference compared to a 1080p panel, but even watching YouTube videos scaled to fit and everything looked fantastic. There's stacks of detail on offer, decent brightness, punchy colours and considerable viewing angles all as standard. Sat next to the Huawei Mate 7's larger screen and the push in colour is immediately obvious from the Samsung.

Zero moans to be had in terms of quality, just a crystal clear image. It looks particularly impressive when handwriting onto the screen using the S Pen, with fine lines and up to 2,048 pressure levels visibly different depending on your use.

However, the screen falls into one notable stumbling block (as does the LG G3): app compatibility. Having been G3 owners for two months, we'd come to miss playing Candy Crush or Papa Pear Saga. Yes, that might sound lame to some, but if you want such apps then a number aren't (yet - and it's been some months) compatible with such high-resolution screens. So keep that in mind. And a call to developers - sort it out.

Multi-tasking marvels and near misses

Some would argue that the Note 4 is all about enterprise use because of the S Pen. We think it's one of a few devices to succeed on both sides of the fence by doing a fine job of work-related tasks, in addition to gaming, snappy browsing, catching up on the news and so forth. Granted some gaming apps won't work, but when they do the Qualcomm Snapdragon 805 processor and 3GB RAM makes light work of them. The Note 4 is the first device to arrive in the UK with this top-of-the-line processor and it delivered Angry Birds Go! in fluid style.

With power comes responsibility, so they say, and with the Note 4 the oodles of power available means multi-tasking is its forte. Unlike most other phones we've used (save for its predecessors), the Note 4 has a variety of ways to utilise more than one app simultaneously across its large screen real-estate. It's here the resolution makes particular sense for those down-sized app windows, without affecting text legibility.

Press-and-hold the back button and a strip of compatible multi-window apps will open. These range from Facebook to Firefox, through to Messages, My Files, Play Store and many others besides. From here you can arrange two chosen apps above and below one another. A circular virtual nodule to the centre of the active app window can be pressed for size adjustment so one app can fill more space than the other to suit your needs.

There are others ways to access multi-tasking too. Within a compatible app simply swipe from the top left or right corner to the centre of the screen (although this won't work with the S Pen in use, annoyingly) and the application will shrink into a floating version at a smaller scale. The idea is nice, but this particular way forces apps to constrain the screen proportion, so a shrunken webpage will be far taller than wide, which is less than ideal. Also sometimes when swiping downwards from the top left to view notifications the app gets over-excited and will shrink when that wasn't your intended goal. So sometimes things can get fussy.

Multi-tasking doesn't, however, include every app under the sun, so some apps are either full-screen when in use or otherwise out of sight. Our TomTom MySports app, or Samsung's own S Health are two such incompatible examples among many. An easy way to tell is by opening the active apps screen - it's one touch of the menu button - where any compatible app will feature the multi-window symbol to the top right corner of its tab. Tap that and it will open it in a default half-screen arrangement, avoiding the constrained proportion issue highlighted before.

Perhaps most fun of all, though, is the ability to reduce an open app into a floating circular icon - a bit like a Facebook Messenger Chat Head - anywhere on the home screen. Because these floating circular alerts are always on top and can be repositioned at your whim, when you're done being distracted with your first task you can tap the small icon and pick up where you left off. It's a cool idea, but can be long-winded as you'll first need to get an app into shrunken or half-screen arrangement before then clicking the circular nodule and then pressing the icon button. Apps that can't be multi-tasked also aren't eligible, so there is a limit to its use. With some compatible apps stability isn't quite there either (yes, we're looking at you Firefox).

So there might be small tweaks we would make to the multi-tasking system for a more fluid overall functionality in places, but in terms of what's on offer it's streets ahead of any other phone out there - and for that it can only be praised.

S Pen power

Pop the S Pen out of its holding cavity - again, it's a bit plasticky, which is a shame but does make it easy to grip its small size - and the Note 4's functionality steps up to yet another level. Even though the S Pen looks and feels largely similar to that of the Note 3, in the Note 4 it can do that much more. There are now 2,048 pressure levels for a more refined "real pen" feel, plus virtual calligraphy and fountain pen nibs have been added for more creative uses when writing notes directly onto the screen. You'll probably stick with the standard pen more often than not for the functional stuff.

And if a stylus isn't for you then you can all but ignore the S Pen and use the phone without thinking more about it. But it's worth reading this section to see what you'd otherwise miss out on.

Principal to the S Pen feature set is handwriting input (including conversion into text), plus text and image selection tools. This is aided by a pop-up Air Command control centre to access Action Memo for Post-It-style notes, Smart Select to click-and-drag selections for later use from Scrapbook (plus Image Clip for free-hand manual selection), and Screen Write for taking a screen grab for making hand-drawn notes on.

With the Smart Select option in play it's possible to use the S Pen to draw an area around the current screen and this specific area will be saved. But rather than it vanishing into a gallery a small floating widget will remain open so this grab can be easily dragged into a current email, Messenger conversation and such like. Metadata is also carried over, so a selection from a map can be reopened in the necessary Maps application, for example, rather than being a static piece of copy.

Air Command is a great access point, but it doesn't replace the other important S Note feature, rather supplements it, which is where things get a little convoluted. The S Note features now come available as a separate widget to access related files or load a new pen/photo/text/voice-based Notes. Surely S Note management appearing on Air Command would just make sense? Multiple routes into software features has its benefit, but can also make things feel a little maze-like, particularly at first - so newcomers stick with it, it will all coome together in the end.

The power of Notes is more advanced this time around. A nifty feature is Snap Note that can be used to import a camera snap into the phone, auto-adjust any skew and then and convert it into image-like "pen strokes" for further manipulation. Say you shoot some sketched illustrations on a sheet of paper, for example, these can then be imported, selectively deleted and edited, or even enlarged/shrunk as you would a vector image in much of Adobe's high-end software. The only downer here is that text can't be converted into actual text via this method, so there's no way of auto-converting written notes off-device into written ones on it.

Handwriting directly onto the device can be converted into text though, which functions really well. We have crappy handwriting and the Note 4 almost never failed to correctly convert our scribbles into far more legible text. As we said of the Note 3, it would be able to convert even the scrawl of your local GP into proper text.

Voice recordings also listen in real-time and convert what you say into text, but with limited accuracy rather than word-for-word perfection. It's not so much inaccurate listening, more that sections of what you say are ignored, but it's useful for rough notes.

So whether you want to draw, scribble, write, convert, copy specific sections of text or images, the Samsung Galaxy Note 4 is a powerhouse like no other in this department.

Android with TouchWiz

We seem to have written the Galaxy Note 4's software features half to death, but it's these functions that make the Note 4 so distinct. In terms of operating system the Note 4 runs Android 4.4.4 but is fairly heavily reskinned with Samsung's TouchWiz interface and apps. It's much like the Samsung Galaxy S5 smartphone, albeit with a lighter, whiter colour palette and slightly smoother operation.

In addition to all the usual Android goodies, swipe to the left of the homepage and FlipBoard - the news aggregator, presented like a digital newspaper - will load. You can select the kinds of stories you'd like to read, including News, Tech, Business, Food, Travel and more. Only you can't specify your sources, that's all done for you. So the Telegraph and Guardian dominate our feed, and as much as we like them, we have no additional say in the matter. Not that you have to use FlipBoard at all, but it delivers a visually fresh way into content.

Elsewhere there's a whole bunch of Samsung software, from the useful such as S Health and Galaxy Gifts for freebies such as six months of Deezer music, through to the less useful lists of apps that you'll probably never want nor need to look at. But it's not forced upon you as heavily as earlier TouchWiz iterations and we're totally fine with that. The main thing we'd change for a screen of this size is the ability to have five icons across the screen width rather than just four.

Just like the Galaxy S5 there are other headline features. Given the Note 4 is the first Snapdragon 805 chip to the UK market (the Mate 7 shouldn't be far behind), it can manage 4G LTE-A download speeds up to a theoretical 300Mbps. Add the Download Booster that allows for 4G and Wi-Fi to simultaneously download files and things are very speedy indeed. Just make sure your provider's data package is fair to avoid insane download costs.

Healthy living

Since 2013 one of Samsung's big moves has been its approach to the growing health and activity tracking market. We tested the Note 4 as a standalone device where it can track steps, measure heart rate and aid you in achieving various goals. How much you invest with it is entirely optional, but we like the pedometer's step read always showing on the locked home screen.

The heart-rate monitor has limited use though as it's a rear sensor that you'll need to specifically engage with. If you want real-time tracking then you'll need to sync with a Samsung-supported device, such as the Gear Live smartwatch with its wrist-based heart-rate monitor. That's most likely Samsung's end-game here: a fuller ecosystem of devices.

Pocket-lint

We've been checking our pulse levels against a couple of sports trackers, and despite sometimes coming in a little bit low - a couple of 50/51bpm measures are certainly erroneous for us - the heart-rate read was roughly consistent with our TomTom Multi-Sport Cardio.

Step-tracking seemed really accurate and related to actual steps. Fling the Note 4 around on the spot and its built-in sensors know it's not relevant step-based motion. Walk around and you can watch each step increment with each pace which is cool.

However, without full-time heart-rate monitoring we would call into question the accuracy the supposed calorie burn of some of the exercise options. There are running, walking, cycling and hiking options, assisted by accelerometer, gyro, GPS and altimeter sensors for relative accuracy, but without ability to measure wind resistance, cadence and real-time heart-rate the 75-minute cycle we did was hundreds of calories short of both TomTom and Polar measures. Fine as a rough idea, but if you want specific accuracy then you'll want to look elsewhere (for now, anyway, as in the future Samsung may have all the necessary compatible kit).

Battery performance

As much as we walked, ran and cycled in any one day we got tired, but the Samsung Galaxy Note 4 kept on going. This is one device capable of outpacing our waking hours per charge thanks to its 3220mAh battery capacity.

Day one saw a huge amount of updates and downloads as we migrated to the phone, followed by a GPS-tracked 75-minute ride, some gaming, loads of testing and pretty much non-stop use. From 08:30 to 23:30 drained the battery to seven per cent, without any screen brightness dimming or low-power consumption intervention. And that was with Download Booster on too.

Day two didn't need the heaps of downloads and updates so it faired even better, delivering from 06:30 to 23:30 with 35 per cent battery remaining at the end of the day. While it may have less capacity than the Huawei Ascend Mate 7's huge 4100mAh battery, there's no doubting the Galaxy Note 4 can run for a solid day of considerable work and play.

By day three more casual use gave a projected 29-hours of use from the one charge, meaning a day and a half is within reach. If you want more then the Power Saving mode restricts GPS, data and CPU, with screen brightness and greyscale output options also available. There's even a Ultra Power Saving option that turns the Note 4 into a "dumb phone" but keeps it operational for calls and texts for up to two weeks of standby time.

Cameras, 4K and slow-mo

Cameras are a big deal in smartphones and companies know it. There's no mucking about with the Note 4 in this department, as it employs a 16-megapixel rear camera with f/2.4 maximum aperture and 3.7-megapixel f/1.9 front-facing unit to the top right corner. The results are rather impressive too - more so than we expected for a big-screen phone.

Settings and autofocus are handled automatically by default, but there are some manual settings available too should you want to tweak the white balance, adjust the ISO sensitivity (maxes out at ISO 800) and so forth. No aperture or shutter controls, so don't think of it like a high-end camera, but it's a solid example of a point-and-shoot phone camera.

Even when shooting in a dim-lit fireplace the wide aperture of the lens meant a sharp result that was well exposed and despite bumping the ISO sensitivity the shot maintained enough detail even at full scale. It's as good as we've seen from a 16-megapixel smartphone camera.

Video is similar to its predecessor, with options to record in 1080p at 30fps, but there are slow-motion options offering 60fps half-speed, 120fps quarter-speed or even 240fps eighth-speed capture at 1280 x 720 resolution. If you don't want to slow things down then how about 4K (3840 x 2160) capture instead? It's all available here.

We rather like the autofocus toggle on/off during capture and in addition to the running time of a clip a file size counter is also included so you know how many megabytes of storage you're capturing.

The Note 4 takes its predecessor's successes and amplifies them a step further thanks to yet more power. Hats off for that, as it makes for one of the most powerful smartphone cameras out there.

Verdict

The Samsung Galaxy Note 4 is a rare example of a phone that not only does shed loads, but does it all so well. Despite the suggestion of Apple, Huawei and Sony competitors closing in on the big-screen phone space, the Note 4 exists in its own world thanks to S Pen stylus integration and a heap of additional features as a result.

To call the Note perfect would be misleading though. There are still some app excesses, fussy features that could be preened and simplified, the persistent use of budget plastic in a top-tier device baffles us, and the choice of fingerprint scanner technology is not just behind the competition it's also unwieldy in a phone of this size.

But look at it for all its positives and the Galaxy Note 4 can only impress. Not just because it's got a top-tier specification on paper, but because you can see and feel the benefit of that technology in the palm of your hand. No other 5.7-inch screen looks better and even if the competition is beginning to knock at its door the Note 4 can sit back on its throne with its feet up knowing it's done all the hard work. Put simply the Samsung Galaxy Note 4 rules.